VAN = ANALYSE COÛTS-AVANTAGES DES OPTIONS D ADAPTATION EN ZONE CÔTIÈRE À CARLETON-SUR-MER. Executive Summary - PDF

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VAN = ANALYSE COÛTS-AVANTAGES DES OPTIONS D ADAPTATION EN ZONE CÔTIÈRE Executive Summary March ACKNOWLEDGMENTS This study was supported by the Economics Working Group of Canada s Climate Change Adaptation

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VAN = ANALYSE COÛTS-AVANTAGES DES OPTIONS D ADAPTATION EN ZONE CÔTIÈRE Executive Summary March 2016 ACKNOWLEDGMENTS This study was supported by the Economics Working Group of Canada s Climate Change Adaptation Platform, chaired by Natural Resources Canada. It also received funding from Quebec s Green Fund as part of the Climate Change Action Plan. Many people contributed to this study, in particular Pascal Bernatchez and his team at the Laboratoire de dynamique et de gestion intégrée des zones côtières (LDGIZC) of Université du Québec à Rimouski (UQAR), who shared their experience and in-depth knowledge of hydrosedimentary processes of Quebec s coasts and wave dynamics with Ouranos. We wish to thank the city of Carleton-sur- Mer for the precious collaboration of the local committee members. In particular, we would like to acknowledge the invaluable assistance provided by Danick Boulay, Samuel Landry and Karl Leblanc. better understand and integrate the issues at stake within the study area: Josée Michaud (Climate Change Bureau), Nick Xenos (Natural Resources Canada), Jean-Pierre Revéret (UQAM), Adam Fenech (UPEI), Dominique Bérubé (UNB), Élizabeth Marceau (DFO), Graham Frank (Baird), Marcel Roussy (MAPAQ), Rénald Méthot (MAMOT), Jacinthe Girard (MDDELCC), Laurence Laperrière (MDDELCC), Jean-Denis Bouchard (MDDELCC), François Hazel (DFO), Michel Michaud (Transports Québec), Guylène Chouinard (Transports Québec), Hélène Latérière (MCC) et Paul Gingras (MRC La Mitis). Finally, we thank all the organizations and firms that provided essential data for this analysis, especially Pesca Environnement and W.F. Baird & Associates Coastal Engineers. We would also like to acknowledge the contribution of the members of the various committees set up for the project. Among other things, their involvement helped to ANALYSE COÛTS-AVANTAGES DES OPTIONS D ADAPTATION EN ZONE CÔTIÈRE PROJET : ÉVALUATION ÉCONOMIQUE DES RÉPERCUSSIONS DES CHANGEMENTS CLIMATIQUES ET ANALYSE COÛTS-AVANTAGES DES OPTIONS D ADAPTATION EN ZONE CÔTIÈRE AU QUÉBEC Project director: Manon Circé, Ouranos Project delivery team: Laurent Da Silva, Ouranos Xavier Mercier, Ouranos Guillaume Duff, Ouranos François Morneau, Ouranos Claude Desjarlais, Ouranos Ursule Boyer-Villemaire, Ouranos Sylvie Corbeil, AECOM Travis Logan, Ouranos Main collaborators: Pascal Bernatchez, UQAR Steeve Dugas, UQAR City of Carleton-sur-Mer Jean-Pierre Savard, Ouranos Philippe Roy, Ouranos Editing and layout: Beatriz Osorio, Ouranos, and Katherine Pineault, Ouranos Translation: Heather Meek Project number: Suggested citation : Circé, M., Da Silva, L., Mercier, X., Boyer-Villemaire, U., Desjarlais, C. and Morneau, F. (2016) Analyse coûts-avantages des options d'adaptation en zone côtière à Carleton-sur-Mer. Ouranos, Montréal. 169 pages and appendices. (Report available in French only) March 2016 EXECUTIVE summary Few studies to date have focused on the economic assessment of climate change impacts and adaptation options for eastern Quebec s coastal areas. A program of work was therefore initiated by the Economics Working Group of Canada s Climate Change Adaptation Platform, chaired by Natural Resources Canada, to create economic knowledge and tools to help decisionmakers in Canada s private and public sectors make better adaptation investment choices and policy decisions. Under this program of work, the research project Economic Assessment of the Impacts of Climate Change and Cost-Benefit Analysis of Adaptation Options targeted coastal areas of Quebec and the Atlantic Provinces. The Quebec study was conducted by Ouranos and its primary research partner, the Laboratoire de dynamique et de gestion intégrée des zones côtières (LDICZM) of Université du Québec à Rimouski (UQAR), which has developed a wealth of knowledge about coastal erosion and flooding in Quebec. The objectives of the study aimed to assess the economic impacts of erosion due to climate change in Quebec s maritime regions and to analyze the costs and benefits of various adaptation options for coastal erosion and flooding. Five sites were subject to cost-benefit analysis (CBA) in this study: Carleton-sur-Mer, Percé, Îlesde-la-Madeleine, Maria and Kamouraska. This report focuses on the coastline of the city of Carleton-sur-Mer, in Chaleur Bay. Like many other coastal municipalities in Quebec, Carleton-sur-Mer is already experiencing significant climate change impacts, due to sea-level rise, milder winters, loss of ice cover in Chaleur bay and changes in storm patterns. Changes to these hydroclimatic variables accelerate and amplify the hazards of coastal erosion and flooding threatening the land, buildings and infrastructures along the coast. ANALYSE COÛTS - AVANTAGES DES OPTIONS D ADAPTATION EN ZONE CÔTIÈRE 1 methodological APPROACH The purpose of this study is to identify the most beneficial adaptation options for protecting Carleton-sur-Mer s coastal area from the impacts of erosion and flooding hazards, which are increasing due to climate change. The study relies on future erosion projections provided by UQAR s LDGIZC as well as extreme water level projections developed jointly by Ouranos and LDGIZC. The cost-benefit analysis (CBA) compares the aggregated benefits and costs of technically feasible adaptation options, from an economic point of view. The CBA relies on two indicators to compare the adaptation options to nonintervention: net present value (NPV) and costbenefit ratio. The study provides an assessment of economic, environmental and social impacts, as well as the costs of adaptation options. These include preliminary studies, construction and maintenance costs. As for the benefits of adaptation options, most of them stem from avoided costs and from benefits related to the use of the coast. Benefits and costs of proposed adaptation options are discounted at 4% over the study period: They are assessed from a regional perspective for the entire Gaspésie region. STUDY AREA Located in the Chaleur Bay, Carleton-sur-Mer covers a 244 km 2 area in the MRC d Avignon. The current city arised from the fusion, in 2000, of St-Omer and Carleton municipalities and has a population of about 4,000. The study area covers the coast between the heart of St-Omer and the Caps de Maria, on a total length of 29.9 km. It was divided into 8 segments according to the physical characteristics of the coastline and land use. The segments were grouped in 3 sectors, namely Banc St-Omer, Berthelot-Éperlan and Carleton Est. The boundaries of these sectors are identified in Figure A. 2 ANALYSE COÛTS - AVANTAGES DES OPTIONS D ADAPTATION EN ZONE CÔTIÈRE 1 2 3 Study sectors: 1 - Banc St-Omer 2 - Berthelot-Éperlan 3 - Carleton Est ± Figure A - Map of the study area and location of the 3 sectors under study ± adaptation OPTIONS The adaptation options studied in Carletonsur-Mer include hard engineering structures (rubblemounds, embankments, sea walls) and soft engineering structures (beach nourishment with or without groynes, beach nourishment with bioengineering, vegetated sand dunes), as well as an option without coastal structures combining flood proofing and planned retreat when assets are affected by erosion, flooding or both. The adaptation options studied were drawn from a study realised for Ouranos by W.F. Baird & Associates Coastal Engineers (Baird). Taking into account the biophysical, geomorphological and oceanographic parameters of the Carletonsur-Mer coast, Baird conducted a preliminary identification of structures that could protect the Carleton-sur-Mer coastline against 500-year storm events. The main conclusions for each segment are presented below. ANALYSE COÛTS - AVANTAGES DES OPTIONS D ADAPTATION EN ZONE CÔTIÈRE 3 Banc St-Omer SectOr The first sector studied is Banc St-Omer, which covers a distance of 6.5 km from Route Leblanc to Route Beaulieu. It comprises three segments with widely differing coastal issues: Banc St- Omer Ouest, Banc St-Omer Centre and Banc St- Omer Est. The boundaries of these segments are identified in Figure B. The westernmost segment, Banc St-Omer Ouest, is dominated by sand spits and low cliffs of unconsolidated sediment. Close to 90% of the coast is natural. It is expected that, over the next 50 years, 58% of the coast will be eroding, while 42% will be stable or in a slight state of accretion. A total of 80% of the coast will also be subject to flooding. A number of homes have structures to prevent erosion or embankments against flooding. The St-Omer sand bank protects a brackish marshland that is home to a diverse ecosystem of great ecological value. In fact, the St-Omer barachois or lagoon is an Environment Canada protected area. This area also attracts a large number of visitors who practice a wide range of recreational activities. The rear part of this segment, behind the lagoon, contains many homes and businesses in addition to the St- Omer Local community service center (CLSC). Over the time horizon under study, a breach in the spit is expected to occur in 2017, increasing exposure of the buildings in the rear section to the risk of flooding (82 buildings over the study period) and erosion (1 building) hazards. This breach would imply the loss of the protected marshland and of visitor access to the spit. If nothing is done, the CBA indicates anticipated damages estimated at close to $5.9 million, discounted at 4% over 50 years. Almost 62% of these costs are due to the loss of use of the WorldView DigitalGlobe, Inc. Figure B- Boundaries of the 3 studied segments in the Banc St-Omer sector 4 ANALYSE COÛTS - AVANTAGES DES OPTIONS D ADAPTATION EN ZONE CÔTIÈRE spit and 28% to flooding damages. Among the adaptation options studied, beach nourishment with sand is the most advantageous, generating close to $2.7 million in benefits compared to non-intervention. The Banc St-Omer Centre segment, which is about 0.5 km long, is comprised between Rue Caissy and Stewart River. It is almost entirely composed of beach terraces, almost half of which are eroding. While there are few buildings in this segment, the entire coast is subject to flooding episodes which could damage some buildings. In this segment, damages from coastal hazards are estimated to about $724,000 over a 50 years period. Close to 88% of these damages are due to flooding. Flood proofing combined with planned retreat constitutes the most advantageous adaptation option for this segment, although its benefit compared to nonintervention is low, at just over $20,000. The last segment in this sector, Banc St-Omer Est, extends just under one kilometre from the Stewart River to Route Beaulieu. The coast here is quite low, and is mainly composed of beach terraces (58%) and low cliffs of unconsolidated sediment (29%). Even though homes in this segment are not exposed to short term erosion, the probable future erosion rate, in addition to the single-event retreat rate of the cliffs and beach terraces, will lead to damages over the medium and long term. The CBA points to total damages for this segment of close to $160,000, discounted at 4% over 50 years. Erosion, which will affect three buildings, is responsible for just over 90% of these damages. Planned retreat is the most beneficial adaptation option for this segment, although once again the difference between the NPV of this option and that of the nonintervention option is low. Figure C presents the CBA results for all options studied in the Banc St-Omer sector. ANALYSE COÛTS - AVANTAGES DES OPTIONS D ADAPTATION EN ZONE CÔTIÈRE 5 Banc St-Omer Ouest compared to NI Millions Millions Millions $6.0 $5.0 $4.0 $3.0 $2.0 $1.0 $0.0 ($1.0) ($2.0) ($3.0) ($4.0) Banc St-Omer Centre compared to NI $4.0 $3.0 $2.0 $1.0 $0.0 ($1.0) ($2.0) ($3.0) ($4.0) Banc St-Omer Est compared to NI $4.0 $3.0 $2.0 $1.0 $0.0 ($1.0) ($2.0) ($3.0) ($4.0) $2.66 $2.59 Beach replenishment ($1.32) 0.33 Rubblemound revetment ($1.75) ($2.12) ($1.45) Rubblemound revetment Beach replenishment with groynes 1.78 $0.02 Flood proofing and planned retreat Beach replenishment $1.91 Beach replenishment with bioengineering Beach replenishment with groynes $0.08 Flood proofing and planned retreat 1.17 $0.02 Legend Planned retreat compared to non-intervention Benefit/Cost Ratio Figure C - Net present value and benefit-cost ratio of each adaptation option under study per segment B/C Ratio B/C Ratio 6 ANALYSE COÛTS - AVANTAGES DES OPTIONS D ADAPTATION EN ZONE CÔTIÈRE Berthelot-Éperlan SectOr This sector extends for 1.4 km between Rue Berthelot and Rue Landry, all the way to the point where the latter reaches the coast. The rail corridor was excluded from the study, as any intervention to protect this segment should be part of efforts to rehabilitate the entire railway. This sector includes two segments, Rue Berthelot and Ruisseau de l Éperlan, whose boundaries are identified in Figure D. WorldView DigitalGlobe, Inc. Figure D - Boundaries of the 2 segments studied in the Berthelot-Éperlan sector The Rue Berthelot segment is bounded by Route 132 and the railway. Composed of low unconsolidated sediment cliffs, it is a residential area protected by a several metres high rubblemound in good condition. This rubblemound has slowed down coastal erosion, but at the cost of beach loss. Storm waves strike the protective structures with great force, which could eventually cause their collapse. Over the next 50 years, erosion threatens 7 of the segment s 11 homes, but no building is vulnerable to flooding. According to the CBA results, damages in this segment would amount to close to $200,000, 14% of which would be linked to the physical loss of land while 54% would be due to the demolition of 3 homes. In this segment, the non-intervention option requires protecting the access route from Highway 132 to Rue Berthelot for the street s residents. Non-intervention is ANALYSE COÛTS - AVANTAGES DES OPTIONS D ADAPTATION EN ZONE CÔTIÈRE 7 the least costly option, as planned retreat costs exceeds those of losing the homes exposed to erosion over the next 50 years. The Ruisseau de l Éperlan segment extends over almost 1 km between Chemin de la Mer and Rue Landry. The stream s delta lies in the centre of the segment, bordered by a beach terrace and flanked on either side by unconsolidated sediment cliffs. With a retreat rate between and m per year, this segment is at risk of erosion and two-thirds of its coast is artificialized. A number of cottages and trailers have been set up along the top of the cliff to the west of the stream, while to the east there are primary residences exposed to erosion. For this segment, the CBA indicates that discounted damages over the next 50 years would total approximately $300,000. As is the case for the Rue Berthelot segment, all adaptation options studied for the Ruisseau de l Éperlan segment are more costly than non-intervention. Figure E presents the CBA results for the adaptation options studied in the Rue Berthelot and Ruisseau de l Éperlan segments. Rue Berthelot compared to NI Millions $0.0 ($1.0) ($2.0) ($3.0) ($2.05) 0.08 ($0.42) B/C Ratio Legend compared to non-intervention Benefit/Cost Ratio ($4.0) Rubblemound revetment Planned retreat 0.00 Ruisseau de l Éperlan compared to NI Millions $0.0 ($1.0) ($2.0) ($3.0) ($2.67) ($2.66) ($2.60) ($0.26) B/C Ratio ($4.0) Rubblemound revetment Beach replenishment Beach replenishment with groynes Planned retreat 0.00 Figure E - Net present value compared to non-intervention and benefit-cost ratio of each adaptation option under study per segment 8 ANALYSE COÛTS - AVANTAGES DES OPTIONS D ADAPTATION EN ZONE CÔTIÈRE Carleton Est SectOR The Carleton Est sector covers a stretch of more than 10.6 km in the heart of the city of Carletonsur-Mer, and contains the most important services and infrastructures. This sector includes three segments with very different coastal dynamics: Plage municipale, Pédoncule and Caps de Maria. Figure F identifies the boundaries of each segment. To the west, the Plage municipale segment runs close to a kilometre from Rue de la Gare to the Carleton wharf. Carleton s municipal beach is located on a spit and is historically under accretion, nourished by sediments from Ruisseau de l Éperlan and the nearby unconsolidated sedimentary cliffs. However, the last 200 m of beach before the wharf are eroding (-0.21 m/year) and the section before the wharf is artificialized. WorldView DigitalGlobe, Inc. Figure Boundaries of the 3 segments studied in the Carleton Est sector This segment experiences problems with flooding caused by direct surges along the waterfront and breaking waves to the east of the wharf. Over a period of 50 years, some thirty buildings and infrastructures in the western part of the segment will be affected by flooding events. The road leading to the Carleton wharf is also subject to flooding, but the episodes are not long enough to lead to economic losses by compromising the activities that depend on wharf access. According to the CBA results, the cost of inaction on the time horizon under consideration would amount to $6.1 million, 74% of which would be damages associated with flooding. Among the ANALYSE COÛTS - AVANTAGES DES OPTIONS D ADAPTATION EN ZONE CÔTIÈRE 9 adaptation options studied for this segment, flood proofing of buildings proves to be the most advantageous, producing a net benefit of $1.85 million compared to non-intervention. Located on the municipal campground sand spit that shelters the Carleton lagoon, the Pédoncule segment extends for 1 km from the start of the neck of the spit (thinnest section at the landward end of the spit) to the curve in the campground road. To protect it from the erosion and flooding hazards during storms, two-third of the segment has been artificialized, mainly by rubblemound and wooden sea walls. Despite the sediment contribution from the capes of Maria, the coastal dynamic in this location does not allow accumulation. If nothing is done, erosion could cut through the neck of the spit by around 2040, preventing road access to the campground and resulting in the loss of camping-related revenues. The results of the CBA show that the damages associated with inaction, discounted at 4%, would amount to $3.25 million over 50 years in this segment. Among the adaptation options studied, beach nourishment with groynes is the most advantageous option, providing a net benefit of just over $1.24 million. The Caps de Maria segment stretches on 5.4 km from Avenue du Phare to Auberge des Caps. It is essentially composed of unconsolidated sediment cliffs some 20 to 30 m in height, which are eroding at a rate varying between m and m per year. The resulting sediment contributes to replenishing the Carleton lagoon sand spit. This segment is therefore essential for slowing down the creation of a breach in the neck of the spit in the Pédoncule segment. Over the time horizon under study, erosion is expected to lead to the loss of a strip of land 14 to 35 metres wide, which will affect some thirty homes located at the top of the cliffs. Despite these potential losses, the CBA results indicate that non-intervention constitutes the least costly option for this segment with discounted costs evaluated at around $1.54 million. Planned retreat in this location would involve additional costs of $1.37 million. Figure G presents the results of the CBA for all adaptation options studied in the Carleton Est sector. 10 ANALYSE COÛTS - AVANTAGES DES OPTIONS D ADAPTATION EN ZONE CÔTIÈRE Plage municipale compared to NI Millions $4.0 $3.0 $2.0 $1.0 $0.0 ($1.0) ($2.0) 0.91 ($0.61) 1.68 $ B/C Ratio ($3.0) 0.25 Pédoncule compared to NI Millions ($4.0) $4.0 $3.0 $2.0 $1.0 $0.0 ($1.0) ($2.0) Multiple protections 0.53 Flood proofing 1.07 $ $ B/C Ratio Millions ($3.0) ($4.0) Caps de Maria Ouest compared to NI $4.0 $3.0 $2.0 $1.0 $0.0 ($1.0) ($2.0) ($3.0) ($4.0) ($2.83) Road flood pro
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